# A081470 (b-file synthesized from sequence entry)
1 2
2 12
3 120
4 1680
5 30240
6 504
7 17297280
8 11880
9 3603600
10 360360
11 28158588057600
12 43680
13 64764752532480000
14 586051200
15 1860480
16 53721360
17 830034394580628357120000
18 96909120
19 4299578163927654889881600000
20 6375600